1. Field of the Invention
The present invention is related to a polymer which is suitable for use in a diagnostic product, a test drug, or a liquid chromatography, particularly to a polymer which is suitable for use as a ligand immobilization support. The ligand immobilization support utilizes the affinity chromatography principle and is suitable for separation or purification of a valuable substance or a disease agent in a liquid, such as an antibody.
2. Description of the Related Art
A purification technique called “affinity chromatography” has been reported (for example, in “Immobilized Affinity Ligand Techniques”, (Academic Press, 1992), the disclosure of which is incorporated herein by reference). In the technique, a substance (ligand) having an affinity to the target substance to be purified or to be separated is immobilized on an insoluble polymer, and the target substance is specifically adsorbed by the ligand and collected. For the purification of antibodies, methods have been disclosed such as a method (see, for example, Japanese Patent application Laid-Open (JP-A) No. 7-146280, the disclosure of which is incorporated by reference herein) using an affinity gel in which κ light-chain binding protein is bonded to an agarose gel, or a method (see, for example, JP-A No. 6-34633, the disclosure of which is incorporated by reference herein) using a support obtained by immobilizing a ligand (antibody) on a water-insoluble cellulose through an epoxydation reaction with a hydrophilic spacer having epoxy groups at both terminals thereof.
If a support gel derived from a natural product such as agarose is used, however, the gel itself dissolves at 40° C. or higher and is not stable when the temperature is changed. Moreover, a highly toxic agent such as epichlorohydrin has to be used in order to synthesize epoxydated cellulose from cellulose. The synthesized epoxydated cellulose binds to functional groups on the ligand with a low selectivity. Therefore, the epoxydated cellulose binds also to the moiety on the ligand having the affinity to the target substance. As a result, the affinity of the ligand on the support is not strong. Further, the purity of the support gel such as agarose or cellulose is low since such materials are derived from natural products.
A ligand immobilization support has been disclosed in which a ligand and a support are bonded to each other by a disulfide bond. The following can be referenced: JP-A No. 2004-45120 (the disclosure of which is incorporated herein by reference) and “Immobilized Affinity Ligand Techniques”, (Academic Press, 1992). However, the disulfide bond is chemically unstable and easily cleaved in the presence of other compounds (such as peptides and proteins having cysteine moieties) having thiol groups.
Immobilization supports have been disclosed (for example in JP-A Nos. 6-34633 and 2004-45120) which are synthesized polymers such as: a polystryrene or polymethacrylic acid having functional groups (such as a thiol group, an amino group, a hydroxyl group, and a carboxyl group), a derivative thereof, and a copolymer thereof; polyvinyl alcohol; and styrene-divinylbenzene copolymer. However, the above general synthesized polymers have problems. For example, if the immobilization support is an aliphatic polymer such as polymethylmethacrylate or polymethacrylic acid, the performance on antibody separation is very low. If the immobilization support is an aromatic polymer such as polystyrene or hydroxymethylpolystyrene, the selectivity is low and antibodies other than the target antibody are also adsorbed nonspecifically.